This invention relates to a solder-bearing lead for attachment to a substrate or integrated circuit chip or other circuit device, having a discrete mass of solder mechanically held by the lead in position to be melted for connecting the lead to the circuit device with both an electrical and mechanical bond. The invention also relates to a dual solder-bearing lead arrangement for attachment to an insulated holder, or substrate, and having a terminal pin arrangement for subsequent attachment to another substrate or a chip for connecting them to one another.
The lead of the present invention is of a type which is capable of being continuously formed by a progressive stamping apparatus from a thin strip of metal at high speed, and because each lead mechanically holds its own discrete mass of solder, the leads may be produced individually or preferably are attached to a common carrier strip for automated machine insertion into mating receptacles in a substrate or holder or for application to the surface of a substrate.
Various means have been previously provided where a quantity of solder is associated with a lead so that when the lead is juxtaposed to a substrate (usually with a corresponding conductive surface area or pad with which the lead is to be connected), and the assembly is heated, the molten solder covers the juxtaposed surfaces of the lead and substrate to form, when cool, a soldered joint forming an electrical and mechanical connection between the lead and substrate.
In the prior art, in one form a solder mass or slug was associated with a lead by means of a metallurgical or mechanical bond between the solder and the lead, with the solder positioned with the lead between it and the conductive area in the substrate. This method suffered from inconsistent solder bonds because the molten solder was required to migrate to reach the junction between the lead and the region to which the lead was to be soldered.
In some arrangements the solder mass is held mechanically against the lead by various tabs or fingers, formed from the body of the lead. The present invention constitutes an improvement on such arrangements. Examples of such other arrangements may be seen in U.S. Pat. Nos. 4,120,558; 4,203,648; 4,592,617; 4,697,865; 4,728,305; 4,738,627; 4,883,435; 4,932,876.